My "new" 1990 740 turbo and I were headed to the salvage yard today. After 1 hour driving at 75 mph in 95 degree heat the engine lost all power then stalled. On the side of the highway the car would start but sputtered and stalled several times. I unplugged the AMM and no real change. I checked the fuses and they are ok. According the the temp guage in the car was not overheating. After 1/2 hour the car started and I drove about 1 mile before it stalled. 20 min later it started and I drove 2 miles. 1.5 hours later I drove for 1 hour between 55 - 70 mph to my house.


I have only had the car for 4 days so I don't have any history but the out of tank Fuel pump is making more noise than I think it should. Also, the car seems sluggish compared to what I remember my last 740 turbo was like.

From reading the FAQ section I think I'll try to check the Fuel Pressure Regulator any other suggestions? I am also thinking that the heat may have caused the fuel pump to seize...is that possible?

Thanks for your help!

After changning the fuel filter, external fuel pump, and the power stage chip, I changed the in tank fuel pump and added a new strainer. I haven't had time to test the car in depth but the whining sound from the external fuel pump is gone and the car is starting and driving with out incident. Hopefully, no more surprises on the highway.

Total cost in used parts $50.00 but of course I spent 170 buying some really great other parts like a center console cup holder and wheel covers!

Thanks to everyone for the suggestions.

Hey Chad,


Glad to hear that the pump noise is gone. Good luck with your car. I hope it runs well with no unpleasant surprises.



Regards, Jon

I am having the exact problem her in the HOT weather in New Mexico.

http://www.brickboard.com/RWD/volvo/1292734/220/240/260/280/1983_dl_stalling_hot_weather.html

Thanks for the suggestions. I was sure you were right about the power stage chip. I removed it and found that it is an aftermarket chip and it had good themal grease under it. The connection was full of electic grease. It still may be the problem so next time I am in the salvage yard I'll pick up a spare.

Any other suggestions are greatly appreciated!

I don't know how similar your car is to my now-deceased 1986 764T, but I had yoru scenario happen on numerous occasions. One fateful time it was on the West Side Highway in NYC. Not fun. It made it 3/4 of the way home to Boston, only to have to be towed the last 60 miles or so. Again, not fun. In this case it was the power stage chip, that sits on the inside of the fender and as Jon has said it is prone to failure. I replaced three in about a year's time. The aftermarket did not last nor did the replacement Bosch. I used to carry a spare with me after the above incident.
--
1991 745

Hey Chad,


When you are referring to the fuel pump, which one are you referring to?
There are two. One is a lift pump in the tank, and there is another under the car on the drivers' side ahead of the rear wheel that provides pressure to the FI system. If the main pump seized, the car would not run. Try to see which is noisy.
If its weak, that may be reducing engine power. Methods of checking pressure are described in the FAQ and in many manuals. But before condemning the pump, replace the fuel filter. You will also need the hose that connects it as well, since they break when you change the filter. FCP Groton has the hose and filter. The filter is about ten bucks and the hose is about thirty. Check your other tune up items as well.


Regards, Jon

Thanks for the help!

I drove the car to work and back today. No problems. Parked the car for a couple of hours and then tried to move it. It started and then stalled. Couldn't get it running all afternoon.


So just for fun....I replaced the external fuel pump (it was the one making unhappy noises) I also replaced the fuel filter at the same time. The fuel pump sounded great when I turned the key to the II position but as soon as the car started it began making the same buzzing / whining noises. Not the usual operating sounds.

Chad

Hey Chad,


The problem you have is likely an issue with the in-tank pump or its hose. The under car pumps can make noise if there is a hole in the hose (which often happens), they can also make noise if the in-tank pump getting worn or is not working. A in-depth description about troubleshooting is in the FAQ under 'Fuel System'. If you get into the fuel tank, replace the hose and the filter sock that goes on the pump. This is also explained better than I can in the same section of the FAQ. You said that the car still stalls, this is most likely the power stage as we discussed before. Changing the filter was a good start. You may have not needed to change the pump, but if was the original, it was likely tired.


Best regards, Jon

Hey Chad,


What you are experiencing sounds like a failing power stage to me. That is what often causes stalling at speed, then restarting after a cool down. Take a look at the FAQ in the ignition system area about the power stage. Its located on the driver side inner fender toward the front, its screwed onto an aluminum heat sink. It needs to have thermal grease on the entire mating surface. If the grease is dried out, you can get it at radio shack or computer supply store. This grease is important. It transfers the heat from the power transistor to the heatsink. If its dried out and chalky, remove it with alcohol (from both the power stage and heatsink) and reapply it. Make sure the screws are firmly tightened. However, chances are the power stage is original and needs replacement. I would recommend getting a genuine Bosch one at FCP Groton (www.fcpgroton.com. The aftermarket part is a tempting way to save money, but are more prone to fail prematurely. The Bosch one costs about $82.00. I don't think your fuel pressure regulator is causing your trouble. If no fuel/odor comes out of the hose, its most likely fine. The pump may be getting on in years, but I don't think thats your issue here. Any further suggestions are welcome.

Regards, Jon 'Uncle Olaf'